The project has two primary objectives: (1) to study the dispersion of monodisperse aerosols by oscillatory flows in glass models of human tracheobronchial trees and hollow lung casts and (2) to study the local rate of deposition of aerosol particles from flows in branching systems with dimensions based on anatomical data of the bronchial tree. We plan to investigate the effects of such variables as flow rate, inhaled volume, particle size, airway dimension, and configuration of airway trees. For the dispersion study, two approaches will be used: (1) to treat the branching system as a black box which can be investigated by the stimulus-response technique and (2) to investigate the instantaneous position and shape of aerosol boluses in the branching system. Our long term goal is to develop mathematical models for the dispersion and the deposition of inhaled particles in the upper respiratory tract. Such theoretical models will have application in estimating local rates of particle deposition in the lungs. This, in turn, will better our understanding of the health effects of particulate air pollutants. Furthermore, the mathematical lung models will have application in studies of pulmonary functions and inhalation therapy.